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JEE Main20208 Jan 2020Morning ShiftMathematicsSequences and SeriesActual

The sum ∑ k = 1 20 1 + 2 + 3 + … + k is ___________.

Correct answer

0

Step-by-step solution

        ∑ k = 1 20 k ( k + 1 ) 2 = 1 2 ∑ k = 1 20 k 2 + k = 1 2 20 21 41 6 + 20 21 2 = 1 2 420 × 41 6 + 20 × 21 2 = 1 2 2870 + 210 = 1540

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